The background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
In the last 30-40 years, the trend in the refining industry has been to design and optimize Crude and Vacuum Units to process heavy crudes. However, with the development and adoption of fracking technology, lighter crudes are becoming increasingly available. As a result, existing units as exemplarily illustrated in Prior Art FIG. 1 often must be retrofitted to process lighter crudes (e.g., Bakken crudes) since lighter crudes typically require higher operating pressures to maintain the lighter components in the liquid phase. Alternatively, or additionally, vaporization of the lighter components will increase the throughput volume, which in most cases leads to increased backpressure that can be damaging to the unit and may decrease overall throughput and quality of the processed crude.
To overcome at least some of the difficulties associated with lighter components in a crude feed, a pre-processing train may be retrofitted to include a preflash drum as exemplarily shown in Prior Art FIG. 2. However, the vapor phase form the preflash drum is typically fed to the crude or vacuum unit and as such adds throughput volume on the crude or vacuum unit. Moreover, the preflash drum does generally not provide for a separation of the vapor and liquid phase that would produce the vapor phase as a value product. Better separation efficiency can be obtained using a preflash column as is exemplarily shown in Prior Art FIG. 3. Here, the crude feed is subjected to a steam stripping/separation column that produces a liquid naphtha fraction that can be used as a value product or feed to another processing plant, and the liquid phase is fed to the crude or vacuum unit. While such systems advantageously allow for withdrawal of some of the vapor phase, pressure increase in the preflash column may still be an issue.
Still other configurations and methods as, for example, described in U.S. Pat. No. 4,082,653 teach a system with multiple flash zones where the vapors and the liquids are all fed into a downstream crude column. While such system provides certain advantages, the multi-flash arrangement of the '653 patent will generally not resolve the issue of excess vapor production. Similarly, US 2011/0168523 describes a system with two flash zones for two distinct feeds for a crude unit and a vacuum unit. Once more, such system is generally inappropriate both as a retrofit and as a stand-alone system to accommodate preprocessing of light crude. All publications identified herein are incorporated by reference to the same extent as if each individual publication or patent application were specifically and individually indicated to be incorporated by reference. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.
Thus, even though various systems and methods for pre-processing crude are known in the art, all or almost all of them suffer from one or more disadvantages. Therefore, there is still a need to provide improved systems and methods of pre-processing of lighter crude oil prior to entry into a crude or vacuum unit.